The idle reduction vehicle has a possibility of power shutdown of electronic parts due to a voltage drop of a battery, when restarting an engine after idle reduction. The power shutdown of the electronic parts while an ignition switch is on gives uncomfortable feeling to a driver.
In response to the above, Patent document 1 discloses a technique of suppressing the voltage drop of the battery at the time of starting the engine by interposing a rush current suppression circuit, in which a resistor and a bypass relay are connected in parallel, between a battery and a starter motor, and by closing a normally open contact of the bypass relay after a lapse of a predetermined period of time after starting the engine.